Flotation process



Patented Jan. 23, 1934 os-Pics 1,944,529 v ino'rs'rron raocass cWilhelm. Schifer and Willy Mertens, Bochum,

Germany, assignors to 1312- und Kohle-Flota- Gesellschaft mit tionBo'chum, Germany beschrankter Bathing, v

:No Drawing. Application January 11, 1933, serial 113151051328, and inGermany September 26,

16 Claims. (01. 209-160) a This invention relates to froth-flotation ofcoal, for the purpose to separate the fusain from the other structuralconstituents of coal namely 'vitrain, clarain and durain.

According to the United States Patent No. 1,499,872, it isknown torender the fusain', which is present in nearly all coals and has anadverse influence on coking, wettable and nonfloatable by the additionof protective colloids such as starch, tannin, albumen or glue, tothecoal slurry in the preparationfof the coal by the flotation .process,whereby itis. necessary to regulate the amount. of said protectivecolloids so that the other structural constituents of the coal retaintheir floatable capacityq nd can be floated out as a product low infusain. These processes have the drawback of being extremely delicate,in

consequence of which the separation of the fusain from the otherstructural constituents of the coal is usually incomplete. If, forexample, the requisite concentration of the protective colloids beslightly exceeded, the depressing action of the protective colloidsextends, to a certain extent,

to the vitrain and durain which then partly pass away together with thefusain. If the concentration of the protective colloids be too low, a

a portion of the fusain will be left in the vitrain and the desireddegree of separation will not water.. These agents may be organic acidchlo- Y be attained.

The object of the present invention is to provide a flotation processenabling'the separation of the fusain from the other structuralconstituents to be effected in a less delicate and more complete manner.

According to this invention fusain is separated from the otherconstituents of coal in a frothfiotation process by adding to the pulpin presence of a froth producing reagent a protective colloid whichdepresses the durain, vitrain and clarain without afiecting thefloatability of fusain. The protective colloids which can be used incarrying out this invention may be polyhexoses [(CsHmOs); such asstarches or dextrins] which have been pre-treated withhydrogen-chloride.

The most effective result can be obtained in treating starches ordextrins with hydrogenchloride in nascent state by adding agents whichsplit off hydrogen-chloride when treated with rides (such asacetylchloride and benzoylchloride) or some suitable inorganic chlorides(such as AlCls and ZnCls).

It has been ascertained that starches or dextrins, pre-treated in thedescribed manner, form "suitable additions which do not affect the floatexceed those required to efiect the depression of 35 the vitrain anddurain constituents, it can be extensively floated ofi after adding afrothlng agent, whilst the other structural constituents of the coalremain unfloatable. The froth producing agents which can be used for thesepara- 7 tion of the fusain may preferably be wood-tar oils of lowboiling point (105-160 Cels.) whilst wood-tar oiis of higher boilingpoint would partly neutralize the depressing action of the protectivecolloids. After separating the froth containing the fusain, theremainingpulp after the addition of a slightly dissociated alkali and one or moresuitable frothing agents is' subjected to a second froth-flotationoperation adapted to separate the so durain, vitrain and clarain fromthe waste. The addition of a slightly dissociated alkali to the pulpafter the removal of the fusain has the eifect of again rendering theother structural constituents floatable. These constituents-can a thenbe floated. off as a product that is low in ash and practically freefrom fusain with the result, that the recovery can be raised to amaximumbecause there is no longer any need to take into consideration thechance of fusain being ner and the resulting froth containing the iusainin a concentrated condition is removed while the other structuralconstituents of the coal remain I in the pulp. After the fusain has beenremoved,

'the slurry is treated with slightly dissociated alkalis, such as.sodium carbonate or waterglass, until dye reaction is neutral orslightly alkaline.

.Finally, the other structural constituents are u.

floated off by the addition of the known oils suitable for coalflotation.

The manner in which the polyhexose pro-treated with hydrogen-chloride,act in the separation of the fusain from the other structuralconstituents of the coal, by the flotation process, will be evident fromthe following examples:-

Example 1.-1000 grams of coal slurry from a Ruhr colliery and with asolid: liquid ratio of 1:4,

were treated with 0.2 grams of dextrin (pre- Product Weight it) Ash 7,)Ash (kgs) Fusaiu product Coal wcowo w-qcc Raw coal The fusain producthas'no caking capacity and cannot be coked. On the other hand, the coalproduct exhibits excellent caking capacity and furnishes a firmmicroporous coke.

Example 2.-1000 grams of dust coal from an English coal deposit werestirred for several 'minutes with about 3 parts of water and theaddition of 0.15 grams of starch (pre-treated with acelyt chloride), andthen floated with the addition of 4 drops acetone-light oil boilingpoint 105-140 Cels.). After the removal of a fusain product, as thefirst batch of foam, the vitrain and fusain were floated off withaddition of 0.3

Products Weight (76) Ash(%) Ash (kgs.)

Fusain product Goal F F i- Mu eum The fusain product exhibited poorcakingcapacity whilst on the other hand, that of the coal product wasvery good.

Example 3.-In the flotation of a slurry of Silesian coal the fusainproduct was first floated off, with addition of 0.2 grms, of dextrin(-pretreated with zinc-chloride), the flotation of the vitrain andfusain constituents being then effected after addition of 0.4 grms ofwaterglass and 5 drops of coaltar oil. The results. are given in thefollowing table:-

Product Weight Ash 9; Ashrk s.)

The recovered fusain product cannot be coked, whereas the coal productfurnishes excellentcoke. It is evident from the above example that thenew flotation process is generally applicable to -,the separation of thefusain from the'other structural constituents of coal. In addition tothe examples given, in which coals from the Ruhr, Silesian and Englishcoal districts were-treated, 80 experiments were also conducted withcoal from Saxony, the Sarre district and Czecho-Slovakia,

and furnished similar good results in respect of separation.

I The quantity of pre-treated dextrins and starches required forcarrying out the-"process ranges in general, between 100 and 300 gramswherein heterogeneous coal is made into 'a'pul-p with water andsubjected to froth-flotation separation in the presence of a frothproducing reagent and of a polyhexose which has been pretreated withhydrogen-chloride.

2. A flotation process for separating fusain from the other structuralconstituents of coal,

'wherein heterogeneous coal is made into a pulp with water and subjectedto froth-flotation separation in the presence of afroth producingreagent and of a polyhex'ose which has been pretreated withhydrogen-chloride in nascent state by adding agents which split ofihydrogen-chloride when treated wit water.

3. A flotation process for separating fusain from the other structuralconstituents of coal, wherein heterogeneous coal is made into a pulpwith water and subjected to froth-flotation separation in/ the presenceof a froth producing n reagent and of a polyhexose which has beenpretreated with inorganic chlorides which split off hydrogen=chloridewhen treated with water.

4. A flotation process for separating fusain from the other structuralconstituents of coal, wherein heterogeneous coal is made into a pulpwith water and subjected to froth-flotation separation in the presenceof a froth producing reagent and of a polyhexose which has beenpretreated with organic acid chlorides.

5'. A flotation process for separating fusain from the other structuralconstituents of coal, 1,20v wherein coal is'made into a pulp with waterand subjected to a froth-flotation separation in the presence of a frothproducing reagent and of starch which has been-pre-treated withhydragon-chloride. 13

6. A flotation process for separating fusain from the other structuralconstituents of coal, wherein coal is made into apulp with water andsubjected to a froth-flotation separation in the presence of a truthproducing reagent and 01 starch which has been pre-treated withhydrogen-chloride in nascent state by adding agents which split oifhyrogen-chloride when treated wherein coal is made into a pulp withwater and subjected to a froth-flotation separation in the presence of afroth producing reagentand of starch which has been pre-treated withorganic acid chlorides. v

9. A flotation process for separating fusain from the other structuralconstituents of coal, wherein heterogeneous coal is made into a pulpwith water and subjected to a froth-flotation operation in the presenceof a froth producing reagent and of dextrins which has been pretreatedwith hydrogen-chloride. I e

10. A flotation process for separating fusain from the other structuralconstituents of coal, wherein heterogeneous coal ismade into pulp withwater and subjected to a froth-flotation operation in the presence of afroth producing reagent and of dextrins which has been pretreated withhydrogen-chloride in nascent state by adding means which split offhydrogen-chloride when treated with water.

11. A flotation process for separating fusain from ithe other structuralconstituents of coal, wherein heterogeneous coal is made into a pulp-with water and subjected to a froth-flotation operation in the presenceof a froth producing reagent and of dextrins which has been pretreatedwith inorganic chlorides which split off hydrogen-chloride when treatedwith water.

12. A flotation process for separating fusain from the other structuralconstituents of coal, wherein heterogeneous'coal is made into a pulpwith water and subjected to'a froth-flotation operation in the presenceof a froth producing reagent and of dentrins which has beenpretreatedwith organic acid chlorides.

13. A flotation process for separating fusain from the other structuralconstituents of coal, wherein heterogeneous coal is made into a pulpwith water and subjected to a froth-flotation operation in the presenceof a small quantity of wood-tar oil of low boiling point and of apolyhexose which has been pre-treated with bydrogen-chloride. V

14. A flotation process for separating fusain from the other structuralconstituents of coal, wherein heterogeneous coal is made into a pulpwith water and subjected to a froth-flotation operation in the presenceof a froth producing reagent and of a polyhexose which has beenpretreated with hydrogen-chloride'; separating the froth containing thefusain and adding to the remaining pulp slightly dissociated alkalis forthe purpose of again rendering the other structural constituentsfloatable.

15. A flotation process for separating fusain from the other structuralconstituents of coal,

wherein heterogeneous coal is made into a pulp with water and subjectedto a froth-flotation operation in the presence of a small quantity ofwood-tar oil of low boiling point and of a polyhexose which has beenpre-treated with hydrogen-chloride; separating the froth contain ing thefusain and adding to the remaining pulp slightly dissociated alkalis forthe purpose of again rendering the other structural constituentsfloatable.

16. A flotation process for separating fusain from the other structuralconstituents of coal, wherein heterogeneous coal is made into a pulpwith water and subjected to a froth-flotation operation in the presenceof a froth producing reagent and of a polyhexose'which has beenpretreated with hydrogen-chloride; separating the froth containing thefusain and again subjecting the remaining pulp after the addition of aslightly dissocc. .ted alkali and a frothing agent to a flotationoperation to separate the durain, clarairi and vitrain from the waste.

WILL-Y MERTENS.

